1. Field of the Invention
This invention relates generally to signal processing in a radio receiver and more particularly to removal of undesired signals received at the radio receiver.
2. Related Art
Numerous communication systems rely on receiving one or more radio frequency (RF) signals. As the available frequency bands become more congested, the numerous radio frequencies used by the different communication systems start to interfere with each other. One type of interference encountered in the different communication systems is carrier wave interference or more commonly called carrier wave (CW) jamming.
CW jamming is a source of interference in spread spectrum systems, such as CDMA cellular telephone systems and satellite positioning systems. Spread spectrum communication systems use lower power signals spread across the frequency spectrum and are subject to interference from carrier waves used in other communication systems. The problem of CW jamming is further complicated because of the geographical area covered by spread spectrum system may include the whole Earth, for example the United States' Global Position System (GPS).
Attempts to eliminate CW jamming signals have occurred by regulating frequency use and by adding dedicated circuitry to radio receivers. The added circuitry being included in radio receivers often result in additional power consumption and expense. Some examples of jamming signal detection approaches and signal performance improvement approaches may be found in U.S. Pat. Nos. 6,448,925, 6,577,271, 6,606,349, and patent application Ser. No. 09/562,749.
Therefore, there is a need for methods and systems for identifying and removing CW jamming signals that overcomes the disadvantages set forth above, and others previously experienced.